Coming late to this, during the C16th and C17th the rapier was indeed noted as being unmilitary, being too long for the battlefield and unable to pierce any form of protection.
However, one reason the introduction of the rapier for use by gentlemen was initially condemned was because a thrust through the body was invariably fatal whereas cuts from broadsword and backsword blades were often survivable. Masters of Defence were expected to prove their mastery via fights with live blades and the 'swashbucklers' would fight with live blades and both would live to tell the tale.
Work by Dr Ismini Pells on pensions claimed and issued to soldiers of both sides during and after the ECW / BCW / WOTK showed that only 4% of those claiming pensions (usual health warnings etc) were due to sword injuries. From that we can either deduce that swords were rarely used (unlikely for example given the preponderance of cavalry during that era and the contemporary accounts of stormings) or that swords rarely inflicated debilitating injuries. I incline to the latter, suspecting that many wounds were treatable cuts.
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